820 research outputs found
Heterogeneity in Distributed Live Streaming: Blessing or Curse?
Distributed live streaming has brought a lot of interest in the past few
years. In the homogeneous case (all nodes having the same capacity), many
algorithms have been proposed, which have been proven almost optimal or
optimal. On the other hand, the performance of heterogeneous systems is not
completely understood yet. In this paper, we investigate the impact of
heterogeneity on the achievable delay of chunk-based live streaming systems. We
propose several models for taking the atomicity of a chunk into account. For
all these models, when considering the transmission of a single chunk,
heterogeneity is indeed a ``blessing'', in the sense that the achievable delay
is always faster than an equivalent homogeneous system. But for a stream of
chunks, we show that it can be a ``curse'': there is systems where the
achievable delay can be arbitrary greater compared to equivalent homogeneous
systems. However, if the system is slightly bandwidth-overprovisioned, optimal
single chunk diffusion schemes can be adapted to a stream of chunks, leading to
near-optimal, faster than homogeneous systems, heterogeneous live streaming
systems
On Resource Aware Algorithms in Epidemic Live Streaming
Epidemic-style diffusion schemes have been previously proposed for achieving
peer-to-peer live streaming. Their performance trade-offs have been deeply
analyzed for homogeneous systems, where all peers have the same upload
capacity. However, epidemic schemes designed for heterogeneous systems have not
been completely understood yet. In this report we focus on the peer selection
process and propose a generic model that encompasses a large class of
algorithms. The process is modeled as a combination of two functions, an aware
one and an agnostic one. By means of simulations, we analyze the
awareness-agnostism trade-offs on the peer selection process and the impact of
the source distribution policy in non-homogeneous networks. We highlight that
the early diffusion of a given chunk is crucial for its overall diffusion
performance, and a fairness trade-off arises between the performance of
heterogeneous peers, as a function of the level of awareness
Size Does Matter (in P2P Live Streaming)
Optimal dissemination schemes have previously been studied for peer-to-peer
live streaming applications. Live streaming being a delay-sensitive
application, fine tuning of dissemination parameters is crucial. In this
report, we investigate optimal sizing of chunks, the units of data exchange,
and probe sets, the number peers a given node probes before transmitting
chunks. Chunk size can have significant impact on diffusion rate (chunk miss
ratio), diffusion delay, and overhead. The size of the probe set can also
affect these metrics, primarily through the choices available for chunk
dissemination. We perform extensive simulations on the so-called random-peer,
latest-useful dissemination scheme. Our results show that size does matter,
with the optimal size being not too small in both cases
Convergence of the D-iteration algorithm: convergence rate and asynchronous distributed scheme
In this paper, we define the general framework to describe the diffusion
operators associated to a positive matrix. We define the equations associated
to diffusion operators and present some general properties of their state
vectors. We show how this can be applied to prove and improve the convergence
of a fixed point problem associated to the matrix iteration scheme, including
for distributed computation framework. The approach can be understood as a
decomposition of the matrix-vector product operation in elementary operations
at the vector entry level.Comment: 9 page
On Spatial Point Processes with Uniform Births and Deaths by Random Connection
This paper is focused on a class of spatial birth and death process of the
Euclidean space where the birth rate is constant and the death rate of a given
point is the shot noise created at its location by the other points of the
current configuration for some response function . An equivalent view point
is that each pair of points of the configuration establishes a random
connection at an exponential time determined by , which results in the death
of one of the two points. We concentrate on space-motion invariant processes of
this type. Under some natural conditions on , we construct the unique
time-stationary regime of this class of point processes by a coupling argument.
We then use the birth and death structure to establish a hierarchy of balance
integral relations between the factorial moment measures. Finally, we show that
the time-stationary point process exhibits a certain kind of repulsion between
its points that we call -repulsion
Easy identification of generalized common and conserved nested intervals
In this paper we explain how to easily compute gene clusters, formalized by
classical or generalized nested common or conserved intervals, between a set of
K genomes represented as K permutations. A b-nested common (resp. conserved)
interval I of size |I| is either an interval of size 1 or a common (resp.
conserved) interval that contains another b-nested common (resp. conserved)
interval of size at least |I|-b. When b=1, this corresponds to the classical
notion of nested interval. We exhibit two simple algorithms to output all
b-nested common or conserved intervals between K permutations in O(Kn+nocc)
time, where nocc is the total number of such intervals. We also explain how to
count all b-nested intervals in O(Kn) time. New properties of the family of
conserved intervals are proposed to do so
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